JP4641709B2

JP4641709B2 - Ultrasonic motor using laminated piezoelectric vibrator and electronic device using the same

Info

Publication number: JP4641709B2
Application number: JP2003207293A
Authority: JP
Inventors: 朗弘飯野; 聖士渡辺; 陽子篠原
Original assignee: Seiko Instruments Inc
Current assignee: Seiko Instruments Inc
Priority date: 2003-08-12
Filing date: 2003-08-12
Publication date: 2011-03-02
Anticipated expiration: 2023-08-12
Also published as: JP2005065358A

Description

【０００１】
【発明の属する技術分野】
本発明は振動体の振動により移動体を摩擦駆動する超音波モータに関し、特に積層圧電振動体を用いた超音波モータおよびそれを用いた電子機器に関する。
【０００２】
【従来の技術】
弾性体の共振モードを利用した超音波モータは制御性に優れ、近年特に精密位置決め用アクチュエータとしても注目されている。特に、各種ステージ用のアクチュエータとしてはリニヤ型の超音波モータが要求される場合が多く、多くのタイプが提案され研究されている。その中でも、矩形板の縦（伸縮）振動と屈曲振動の合成振動を利用した超音波モータは様々なものが研究されている（例えば、特許文献１参照。）。これらの中でも例えば特許文献１に示す様に振動体を積層圧電素子で構成したものは低電圧で駆動できる為、バッテリーで駆動される各種小型電子機器への応用が期待される。
【０００３】
【特許文献１】
特開2000−116162号公報（第４−５頁、第３図）
【０００４】
【発明が解決しようとする課題】
しかしながら積層された各圧電素子の界面に設けられた複数の種類の内部電極を振動体の側面で短絡するため、内部電極は端部（側面側）付近には基本的に設けずに、短絡させたい内部電極毎に側面方向に張り出し電極部を設け、そこを外部電極により短絡していた。ところで、振動体の屈曲振動の歪は屈曲振動の振幅が最大となる腹付近、しかも振動体の幅方向（屈曲方向）の端部、即ち側面位置が最大となる為、上記のような電極構成によると最も効率的に屈曲振動を励振出来る位置で駆動力を発生できず屈曲振動の励振力が弱かった。このため振動体の長手方向の端面で出力を得るタイプの超音波モータでは速度が小さく、また振動体の幅方向の端面で出力を得るタイプの超音波モータでは大きな出力が得られなかった。特に振動体が小型になるとこの影響は大きくなった。
【０００５】
【課題を解決するための手段】
そこで、本発明では複数の圧電素子を積層して振動体を構成し、前記振動体と接する移動体を駆動する超音波モータにおいて、複数の圧電素子間の界面に設けられた内部電極を短絡する外部電極は振動体に発生する屈曲振動の腹近傍を避ける位置に設ける。特に振動体に屈曲振動を励振する圧電素子の少なくとも屈曲振動の腹に位置する内部電極を振動体の幅方向の端部まで設ける。
【０００６】
また、複数の圧電素子を積層して振動体を構成し、振動体と接する移動体を駆動する超音波モータにおいて、複数の圧電素子間の界面に設けられた内部電極は振動体の幅方向中央部近傍もしくは長手方向端部近傍で短絡する。
【０００７】
この様に屈曲振動の歪が最も大きくなる位置である屈曲振動の腹かつ屈曲変位の中立面から最も離れた幅方向端部において圧電効果による歪を発生可能な様に電極を配置するとともに、これら振動の励振に影響の小さな部分で内部電極を短絡する様にすることで強い屈曲振動を励振可能とする。尚、本手段により縦振動の効率的な励振も可能となる。
【０００８】
【発明の実施の形態】
本発明の実施の形態を図面を基に説明する。
【０００９】
図１は本発明の積層振動子１，２０，２６，３２を振動体として用いたリニヤ型アクチュエータの構成例を示したものである。矩形状の積層圧電素子１，２０，２６，３２には突起２ａ，２ｂ並びに支持部材３が設けられている。加圧部材４の軸部４ａは段部を有し、案内板５の案内穴５ａで、軸方向にのみ移動可能に案内されている。突起２ａ，２ｂの下には案内部材８ａ，８ｂに案内された移動体７が設けられ、支持部材３とその凹部が係合する加圧部材４を加圧ばね６で加圧することにより突起２ａ，２ｂと移動体７は接している。
【００１０】
ところで、積層圧電素子１，２０，２６，３２は縦振動と屈曲振動を励振する。例えば図２は積層圧電素子１の長手方向に対する振動振幅の様子を示したものであり、図２（ａ）は縦振動の様子を、図２（ｂ）は屈曲振動の様子を示したものである。縦振動、屈曲振動共に中央部が振動の節となり、この位置に支持部材３が設けられている。また屈曲振動の腹の位置に突起２ａ，２ｂが設けられている。この縦振動と屈曲振動を同時に励振することにより突起２ａ，２ｂは積層振動子１の長手方向の変位と、これと直交する幅方向の変位からなる楕円運動を行い移動体７を駆動する。ところで、ここでは縦一次モード、屈曲二次モードを用いた例を示したが、二つの振動モードの次数に制限を与えるものではなく、他の次数のモードを用いても構わない。また突起２ａ，２ｂの位置も本実施の形態に限るものではなく振動体の長手方向の端面に設けても構わない。更には移動体７を固定し、積層圧電素子１を移動させる構成としても構わない。
【００１１】
以下に本発明の積層圧電素子１，２０，２６，３２の詳細な説明を行うが、共通した目的は屈曲振動を効率的に励振することにあり少なくとも屈曲振動の歪が最大となる屈曲振動の腹位置（図２（ｂ）中９の位置）近傍かつ振動体の幅方向端面付近にまで駆動力が働くように電極が設けられていることを特徴とする。
【００１２】
（実施の形態１）
積層圧電素子１の構成を図３、図４を基に説明する。図４（ｂ）に示す様に、積層圧電素子１は圧電素子１０，１１，１２，１３が積層され一体的に焼結されている。図３（ａ）に示すように、板状の圧電素子１０の上面には、ほぼ各辺の中央で分割された4つの内部電極１４a，１４ｂ，１４ｃ，１４ｄが設けられ、図３（ｂ）に示すように、圧電素子１１の上面には、ほぼ全体に渡って内部電極１４ｅが設けられ、図３（ｃ）に示すように、圧電素子１２の上面にも、ほぼ全体に渡って内部電極１４ｆが設けられ、図４（ａ）に示すように、圧電素子１３の上面には、内部電極１４ａ，１４ｂ，１４ｃ，１４ｄ，１４ｅ，１４ｆと短絡される外部電極１５ａ，１５ｄ，１５ｃ，１５ｆ，１５ｂ，１５ｅが設けられている。
【００１３】
積層圧電素子１において、電極１４ｅはＧＮＤとなり電極１４ａ，１４ｂ，１４ｃ，１４ｄと電極１４ｅで挟まれた部分の圧電素子は屈曲振動を励振し、電極１４ｆと電極１４ｅで挟まれた部分の圧電素子は縦振動を励振する。従って、屈曲振動の腹（図２（ｂ）中９の位置）の位置付近を含む範囲で振動体の幅方向端面まで駆動力が働くように電極が設けられている。但し、圧電素子の分極方向は全て厚み方向であるが、内部電極１４ａ，１４ｄと内部電極１４ｅで挟まれた部分の圧電素子と内部電極１４ｂ，１４ｃと内部電極１４ｅで挟まれた部分の圧電素子は逆方向に分極処理されている。
【００１４】
次に、積層圧電素子１の内部電極１４ａ，１４ｂ，１４ｃ，１４ｄ，１４ｅ，１４ｆの外部への導通方法を説明する。図４（ａ）は積層圧電素子１の上面並びに側面を見た図である。ここで外部電極１５ａ，１５ｄ，１５ｃ，１５ｆ，１５ｂ，１５ｅは、内部電極１４ａ，１４ｂ，１４ｃ，１４ｄ，１４ｅ，１４ｆと短絡されており、積層圧電素子１に駆動信号を供給するものである。積層圧電素子１において、内部電極１４ａ，１４ｂ，１４ｃ，１４ｄには長手方向に引き出し部１４ａ’，１４ｂ’，１４ｃ’，１４ｄ’が設けられ、内部電極１４ｅには引き出し部１４ｅ’が設けられ、内部電極１４ｆには引出し部１４ｆ’が設けられ、各引出し部は夫々積層圧電素子１の長手方向の端面で外部電極１５ａ，１５ｄ，１５ｃ，１５ｆ，１５ｂ，１５ｅと短絡され、更には積層圧電素子１の上面、即ち圧電素子１３の上面に設けられた外部電極１５ａ，１５ｄ，１５ｃ，１５ｆ，１５ｂ，１５ｅまで導通が取られている。
【００１５】
本積層圧電素子１の駆動方法について説明する。外部電極１５ａ，１５ｃ，１５ｄ，１５ｆと外部電極１５ｂの間に所定の周波数の信号を印加する振動体となる積層圧電素子１には屈曲振動が発生する。また外部電極１５ｅと外部電極１５ｂの間に所定の周波数の駆動信号を印加すると積層圧電素子１には縦振動が発生する。そこで外部電極１５ａ，１５ｃ，１５ｄ，１５ｆと外部電極１５ｂの間に印加する駆動信号と、外部電極１５ｅと外部電極１５ｂの間に印加する駆動信号の位相を変えることにより、振動体となる積層圧電素子１の側面は楕円運動するため、積層圧電素子１に設けられた突起２ａ，２ｂと接する移動体７は移動する。二つの信号の位相差を反転させることにより楕円運動の方向も逆転するため、移動体７の移動方向も変わる。ところで、これら信号の印加方法はこれに限ったものではなく、圧電素子の分極方向等に応じて変えれば良い。逆に言えば圧電素子の分極方向も任意であり、例えば圧電素子１０の分極方向は全て同一方向でも良い。
【００１６】
ところで、以上では各内部電極の短絡並びに外部への引出しは積層圧電素子１の側面で行った例を示したが、その手段に限定を与えるものではない。目的の振動モードの歪が最大となる位置付近に内部電極の短絡手段、外部への導通手段を設けないこと、即ち歪が最大となる位置近傍には必ず圧電素子の発生する力が加わるように内部電極を構成することが本発明の目的である。従って、逆にいえば歪が最小となる位置付近で内部電極の短絡、外部への導通を行えば良い。例えば圧電素子の厚み方向に微小な孔(スルーホール)を設け、孔に導電材料を埋め込み内部電極の短絡、外部との導通を行っても構わない。その場合孔の位置は積層圧電素子１の幅方向端面付近は避けて屈曲振動の変位の中立面となる幅方向中央部に設けるか、長手方向の端面に設けるのが良い。長手方向端面は縦振動の歪も発生しないので、縦振動の励振にも影響を与えず屈曲振動、縦振動共に大きな振動が励振できる。この場合、内部電極は積層圧電素子の幅方向端部まで設けることが出来る。
【００１７】
図５，図６は本発明の実施の形態の積層圧電素子の別の例を示したものである。図６（ｂ）に示す様に、積層圧電素子２０は圧電素子１６，１７，１８，１９が積層され一体的に焼結されている。図５（ａ）に示す様に、板状の圧電素子１６の上面には、ほぼ各辺の中央で分割された4つの内部電極２１ａ，２１ｂ，２１ｃ，２１ｄが設けられ、図５（ｂ）に示す様に、圧電素子１７の上面には、ほぼ全体に渡って内部電極２１ｅが設けられ、図５（ｃ）に示す様に、圧電素子１８の上面にも、ほぼ全体に渡って内部電極２１ｆが設けられ、図６（ａ）に示す様に、圧電素子１９の上面には内部電極２１ａ，２１ｂ，２１ｃ，２１ｄ，２１ｅ，２１ｆと短絡される外部電極２２ｂ，２２ｃ，２２ｅ，２２ｆ，２２ａ，２２ｄが設けられている。
【００１８】
積層圧電素子２０において、電極２１ｅはＧＮＤとなり電極２１ａ，２１ｂ，２１ｃ，２１ｄと電極２１ｅで挟まれた部分の圧電素子は屈曲振動を励振し、電極２１ｆと電極２１ｅで挟まれた部分の圧電素子は縦振動を励振する。従って、屈曲振動の腹（図２（ｂ）中９の位置）の位置付近を含む範囲で振動体の幅方向端面まで駆動力が働くように電極が設けられている。例えば、電極２１ｅ,２１ｆにおいて長手方向の中央部幅方向端面付近においては電極が設けられていないが、これは後で示す様に、電極２１ａ,２１ｂ,２１ｃ,２１ｄと外部電極を短絡させる際に電極２１ｅ,２１ｆとの短絡を避ける為の余白であり、この部分は駆動力を発生しないが、屈曲振動の歪が小さい部分であり駆動力への影響は極めて小さい。但し、圧電素子の分極方向は全て厚み方向であるが、内部電極２１ａ,２１ｄと内部電極２１ｅで挟まれた部分の圧電素子と、内部電極２１ｂ,２１ｃと内部電極２１ｅで挟まれた部分の圧電素子は逆方向に分極処理されている。
【００１９】
次に、積層圧電素子２０の内部電極２１ａ，２１ｂ，２１ｃ，２１ｄ，２１ｅ，２１ｆの外部への導通方法を説明する。図６（ａ）は積層圧電素子２０の上面並びに側面を見た図である。ここで外部電極２２ｂ，２２ｃ，２２ｅ，２２ｆ，２２ａ，２２ｄは内部電極２１ａ，２１ｂ，２１ｃ，２１ｄ，２１ｅ，２１ｆと短絡されており、積層圧電素子２０に駆動信号を供給するものである。積層圧電素子２０において内部電極２１ａ,２１ｂ,２１ｃ,２１ｄは屈曲振動の節にあたり、圧電素子の発生力が振動の励振にあまり寄与しない長手方向の中央部かつ幅方向端面付近において、外部電極２２ｂ,２２ｃ,２２ｅ,２２ｆと短絡され、内部電極２１ｅ及び２１ｆは長手方向の一端で夫々外部電極２２ａ,２２ｄと短絡され、更には積層圧電素子２０の上面、即ち圧電素子１９の上面に設けられた外部電極２２ｂ，２２ｃ，２２ｅ，２２ｆ，２２ａ，２２ｄまで導通が取られている。
【００２０】
積層圧電素子２０の駆動方法について説明する。外部電極２２ｂ,２２ｃ,２２ｅ,２２ｆと外部電極２２ａの間に所定の周波数の信号を印加する振動体となる積層圧電素子２０には屈曲振動が発生する。また外部電極２２ｄと外部電極２２ａの間に所定の周波数の駆動信号を印加すると積層圧電素子２０には縦振動が発生する。そこで外部電極２２ｂ,２２ｃ,２２ｅ,２２ｆと外部電極２２ａの間に印加する駆動信号と、外部電極２２ｄと外部電極２２ａの間に印加する駆動信号の位相を変えることにより、振動体となる積層圧電素子２０の側面は楕円運動するため、積層圧電素子２０に設けられた突起２ａ，２ｂと接する移動体７は移動する。二つの信号の位相差を反転させることにより楕円運動の方向も逆転するため、移動体７の移動方向も変わる。
【００２１】
（実施の形態２）
図７、図８は本発明の超音波モータの積層圧電素子の第二の例を示したものである。図８（ｂ）に示す様に、積層圧電素子２６は圧電素子２３，２４，２５が積層され一体的に焼結されている。図７（ａ）に示す様に、板状の圧電素子２３の上面には、幅方向の中央部で長手方向に渡って内部電極２７ｃが設けられ、その幅方向両側に長手方向の中央部で分割された４つの内部電極２７ａ，２７ｂ，２７ｄ，２７ｅが設けられ、図７（ｂ）に示す様に、圧電素子２４の上面には、ほぼ全体に渡って内部電極２７ｆが設けられ、図８（ａ）に示す様に、圧電素子２５の上面には内部電極２７ａ,２７ｂ,２７ｄ,２７ｅ,２７ｃ,２７ｆと短絡される外部電極２８ａ,２８ｄ,２８ｃ,２８ｆ,２８ｂ,２８ｅが設けられている。
【００２２】
積層圧電素子２６において、内部電極２７ｆはＧＮＤとなり電極２７ａ，２７ｂ，２７ｄ，２７ｅとで挟まれた部分の圧電素子は屈曲振動を励振し、内部電極２７ｆと電極２７ｃとで挟まれた部分の圧電素子は縦振動を励振する。従って、屈曲振動の腹（図２（ｂ）中９の位置）の位置付近を含む範囲で振動体の幅方向端面まで駆動力が働くように電極が設けられている。従って長手方向端部付近では圧電素子は駆動力を発生しないが、この部分は屈曲振動のみならず縦振動の励振にも効果が極めて小さい部分である。因みにこれは後で示す様に内部電極２７と外部電極２８を短絡させる際に目的以外の内部電極の短絡を避ける為の余白である。但し、圧電素子の分極方向は全て厚み方向であるが、内部電極２７ａ，２７ｅと内部電極２７ｆで挟まれた部分の圧電素子と内部電極２７ｄ、２７ｂと内部電極２７ｆで挟まれた部分の圧電素子は逆方向に分極処理されている。
【００２３】
次に、積層圧電素子２６の内部電極２７の外部への導通方法を説明する。図８（ａ）は積層圧電素子２６の上面並びに側面を見た図である。ここで外部電極２８ａ,２８ｄ,２８ｃ,２８ｆ,２８ｂ,２８ｅは、内部電極２７ａ,２７ｂ,２７ｄ,２７ｅ,２７ｃ,２７ｆと短絡されており、積層圧電素子２６に駆動信号を供給するものである。積層圧電素子２６において、内部電極２７ａ，２７ｃ，２７ｄ，２７ｂ，２７ｆ，２７ｅは長手方向端面付近において夫々外部電極２８ａ，２８ｂ，２８ｃ，２８ｄ，２８ｅ，２８ｆと短絡され、更には積層圧電素子２６の上面、即ち圧電素子２５の上面に設けられた外部電極２８ａ，２８ｂ，２８ｃ，２８ｄ，２８ｅ，２８ｆまで導通が取られている。
【００２４】
本積層圧電素子２６の駆動方法について説明する。外部電極２８ａ，２８ｃ，２８ｄ，２８ｆと外部電極２８ｅの間に所定の周波数の信号を印加する振動体となる積層圧電素子２６には屈曲振動が発生する。また外部電極２８ｂと外部電極２８ｅの間に所定の周波数の駆動信号を印加すると積層圧電素子２６には縦振動が発生する。ここで外部電極２８ａ，２８ｃ，２８ｄ，２８ｆと外部電極２８ｅの間に印加する駆動信号と外部電極２８ｂと外部電極２８ｅの間に印加する駆動信号の位相を変えることにより、振動体となる積層圧電素子２６の側面は楕円運動するため、積層圧電素子２６に設けられた突起２ａ，２ｂと接する移動体７は移動する。二つの信号の位相差を反転させることにより楕円運動の方向も逆転するため、移動体７の移動方向も変わる。
【００２５】
（実施の形態３）
本発明の実施の形態３の積層圧電素子３２の構成を図９、図１０を基に説明する。図１０（ｂ）に示す様に、積層圧電素子３２は圧電素子２９，３０，３１が積層され一体的に焼結されている。図９（ａ）に示す様に、板状の圧電素子２９の上面には、ほぼ各辺の中央で分割された４つの内部電極３３a，３３ｂ，３３ｃ，３３ｄが設けられ、図９（ｂ）に示す様に、圧電素子３０の上面には、ほぼ全体に渡って内部電極３３eが設けられ、図１０（ａ）に示す様に、圧電素子３１の上面には内部電極３３ａ，３３ｂ，３３ｃ，３３ｄ，３３ｅと短絡される外部電極３４ａ，３４ｄ，３４ｃ，３４ｆ，３４ｂが設けられている。
【００２６】
積層圧電素子３２において電極３３ｅはＧＮＤとなり、電極３３ａ，３３ｂ，３３ｃ，３３ｄと電極３３ｅで挟まれた部分の圧電素子が縦振動と屈曲振動を励振する。従って、屈曲振動の腹（図２（ｂ）中９の位置）の位置付近を含む範囲で、振動体の幅方向端面まで駆動力が働くように電極が設けられている。但し、圧電素子の分極方向は全て厚み方向で同一方向に分極処理されている。
【００２７】
次に、積層圧電素子３２の内部電極３３ａ，３３ｂ，３３ｃ，３３ｄ，３３ｅの外部への導通方法を説明する。図１０（ａ）は積層圧電素子３２の上面並びに側面を見た図である。ここで外部電極３４ａ，３４ｄ，３４ｃ，３４ｆ，３４ｂは内部電極３３ａ，３３ｂ，３３ｃ，３３ｄ，３３ｅと短絡されており、積層圧電素子３２に駆動信号を供給するものである。積層圧電素子３２において内部電極３３ａ，３３ｂ，３３ｃ，３３ｄには長手方向かつ幅方向端面部分に引き出し部３３ａ’，３３ｂ’，３３ｃ’，３３ｄ’が設けられ、内部電極３３ｅには長手方向の端面中央部に引き出し部３３ｅ’が設けられ、各引出し部は、夫々積層圧電素子３２の長手方向の端面で外部電極３４ａ，３４ｄ，３４ｃ，３４ｆ，３４ｂと短絡され、更には積層圧電素子３２の上面、即ち圧電素子３１の上面に設けられた外部電極３４ａ，３４ｄ，３４ｃ，３４ｆ，３４ｂまで導通が取られている。
【００２８】
本積層圧電素子３２の駆動方法であるが、例えば次の二通りがある。外部電極３４ａ，３４ｆと外部電極３４ｂの間に、もしくは外部電極３４ｃ，３４ｄと外部電極３４ｂの間に駆動信号を印加することで、積層圧電素子３２に縦振動と屈曲振動が励振される。駆動信号を印加する電極を切り替えることで縦振動と屈曲信号の位相が逆転し、移動体7の移動方向も変化する。別の方法としては外部電極３４ｂをGNDとして、外部電極３４ａ，３４ｆと外部電極３４ｃ，３４ｄの間に位相の異なる駆動信号、例えば90度もしくは−90度異なる信号を印加することで、積層圧電素子３２に縦振動と屈曲振動が励振される。位相を逆転させることで縦振動と屈曲信号の位相が逆転し、移動体７の移動方向も変化する。
【００２９】
（実施の形態４）
本発明の圧電アクチュエータを用いて電子機器を構成した例を図１１を基に説明する。
【００３０】
図１１は本発明の駆動回路により駆動される超音波モータ1００を電子機器の駆動源に適用したブロック図を示したものであり、積層圧電素子１，２０，２６，３２と、積層圧電素子１，２０，２６，３２に接合され加圧手段６により移動体７と接する摩擦部材２と、これらにより摩擦駆動される移動体７と、移動体７と一体に動作する伝達機構３５と、伝達機構３５の動作に基づいて動作する出力機構３６からなる。ここでは移動体を回転体とし、移動体を回転動作させる例について説明する。
【００３１】
ここで、伝達機構３５は例えば歯車列、摩擦車等の伝達車を用いる。出力機構３６としては、プリンタにおいては紙送り機構、カメラにおいてはシャッタ駆動機構、レンズ駆動機構、フィルム巻き上げ機構等を、また電子機器や計測器においては指針等を、ロボットにおいてはアーム機構、工作機械においては歯具送り機構や加工部材送り機構等を用いる。
【００３２】
尚、本実施の形態における電子機器としては電子時計、計測器、カメラ、プリンタ、印刷機、ロボット、工作機、ゲーム機、光情報機器、医療機器、移動装置等を実現できる。
【００３３】
さらに移動体７に出力軸を設け、出力軸からのトルクを伝達するための動力伝達機構を有する構成とすれば、超音波モータ駆動装置を実現できる。そして、超音波モータ駆動装置としてステージを構成すると、通常の電磁モータを用いたステージに比較して、機構が簡単かつ小型であるとともに、磁化を避ける環境下でも使用できる超音波モータを利用したステージを提供することができる。
【００３４】
【発明の効果】
本発明によれば、積層圧電素子を用いることによる低電圧駆動特性を持ちながら特に屈曲振動を効率的に励振出来るため縦振動と屈曲振動の変位の合成により発生し、出力を生む振動体の楕円運動の楕円の形状も正円に近くなり、大きな推力が得られるとともに高効率な超音波モータが実現できる。そしてこの効果は振動体を小型化した場合に顕著となるため小型で高出力の超音波モータが実現できる。またこれらの振動体を備えた超音波モータを電子機器の駆動源に用いることにより電子機器の小型化、薄型化、低消費電力化が可能となる。
【００３５】
また、本発明の超音波モータの移動体を直接レンズや指針等の出力部材を設けるか、もしくは移動体の動作を伝達機構を介して出力部材を動かせばカメラのズーム機構、オートフォーカス機構あるいは時計等の電子機器へ応用できる。
【図面の簡単な説明】
【図１】本発明の超音波モータにかかわる構成を示す図である。
【図２】本発明の超音波モータにかかわる振動体の振動モードを示す図である。
【図３】本発明の実施の形態１にかかわる超音波モータの振動体の構成を示す図である。
【図４】本発明の実施の形態１にかかわる超音波モータの振動体の構成を示す図である。
【図５】本発明の実施の形態１にかかわる超音波モータの振動体の別の構成を示す図である。
【図６】本発明の実施の形態１にかかわる超音波モータの振動体の別の構成を示す図である。
【図７】本発明の実施の形態２にかかわる超音波モータの振動体の構成を示す図である。
【図８】本発明の実施の形態２にかかわる超音波モータの振動体の構成を示す図である。
【図９】本発明の実施の形態３にかかわる超音波モータの振動体の構成を示す図である。
【図１０】本発明の実施の形態３にかかわる超音波モータの振動体の構成を示す図である。
【図１１】本発明の超音波モータを用いた電子機器を示す図である。
【符号の説明】
１、２０、２６、３２積層圧電素子
２突起
３支持部材
６加圧ばね
７移動体[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ultrasonic motor that frictionally drives a moving body by vibration of a vibrating body, and more particularly to an ultrasonic motor using a laminated piezoelectric vibrating body and an electronic apparatus using the same.
[0002]
[Prior art]
An ultrasonic motor using the resonance mode of an elastic body has excellent controllability, and has recently attracted attention as a precision positioning actuator in recent years. In particular, linear actuators are often required as actuators for various stages, and many types have been proposed and studied. Among them, various ultrasonic motors using a combined vibration of a longitudinal (extension / contraction) vibration and a bending vibration of a rectangular plate have been studied (for example, see Patent Document 1). Among these, for example, as shown in Patent Document 1, a vibration element constituted by a laminated piezoelectric element can be driven at a low voltage, and therefore, application to various small electronic devices driven by a battery is expected.
[0003]
[Patent Document 1]
Japanese Unexamined Patent Publication No. 2000-116162 (page 4-5, FIG. 3)
[0004]
[Problems to be solved by the invention]
However, in order to short-circuit a plurality of types of internal electrodes provided at the interface of the stacked piezoelectric elements on the side surface of the vibrating body, the internal electrodes are not basically provided near the end (side surface side) but are short-circuited. For each internal electrode, an overhanging electrode portion was provided, which was short-circuited by the external electrode. By the way, since the bending vibration distortion of the vibrating body is near the antinode where the amplitude of the bending vibration is maximum, and the end of the vibrating body in the width direction (bending direction), that is, the side surface position is maximum, the electrode configuration as described above is used. According to this, the driving force could not be generated at the position where the bending vibration could be excited most efficiently, and the excitation force of bending vibration was weak. For this reason, the speed of the ultrasonic motor that obtains the output at the end face in the longitudinal direction of the vibrating body is low, and the output of the ultrasonic motor that obtains the output at the end face in the width direction of the vibrating body cannot obtain a large output. In particular, this effect increased as the vibrating body became smaller.
[0005]
[Means for Solving the Problems]
Therefore, in the present invention, a plurality of piezoelectric elements are stacked to form a vibrating body, and in an ultrasonic motor that drives a moving body that is in contact with the vibrating body, an internal electrode provided at an interface between the plurality of piezoelectric elements is short-circuited. The external electrode is provided at a position that avoids the vicinity of the antinode of bending vibration generated in the vibrating body. In particular, an internal electrode located at least at the antinode of the bending vibration of the piezoelectric element that excites the bending vibration in the vibrating body is provided up to the end in the width direction of the vibrating body.
[0006]
Also, in an ultrasonic motor that drives a moving body in contact with a vibrating body by stacking a plurality of piezoelectric elements, the internal electrode provided at the interface between the plurality of piezoelectric elements is the center in the width direction of the vibrating body. Short circuit near the edge or near the end in the longitudinal direction.
[0007]
In this way, while arranging the electrodes so that distortion due to the piezoelectric effect can be generated at the end of the width direction farthest from the neutral surface of the bending vibration and the antinode of bending vibration, which is the position where the distortion of bending vibration is the largest, Strong bending vibration can be excited by short-circuiting the internal electrode at a portion that has little influence on the excitation of these vibrations. Note that this means also enables efficient excitation of longitudinal vibration.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described with reference to the drawings.
[0009]
FIG. 1 shows a configuration example of a linear actuator using the laminated vibrators 1, 20, 26, and 32 of the present invention as a vibrator. The rectangular laminated piezoelectric elements 1, 20, 26 and 32 are provided with protrusions 2 a and 2 b and a support member 3. The shaft portion 4a of the pressure member 4 has a stepped portion and is guided by the guide hole 5a of the guide plate 5 so as to be movable only in the axial direction. A movable body 7 guided by the guide members 8a and 8b is provided below the protrusions 2a and 2b. By pressing the pressure member 4 engaged with the support member 3 and the concave portion with a pressure spring 6, the protrusion 2a is provided. , 2b and the moving body 7 are in contact with each other.
[0010]
By the way, the laminated piezoelectric elements 1, 20, 26, and 32 excite longitudinal vibration and bending vibration. For example, FIG. 2 shows a state of vibration amplitude with respect to the longitudinal direction of the multilayer piezoelectric element 1, FIG. 2 (a) shows a state of longitudinal vibration, and FIG. 2 (b) shows a state of bending vibration. is there. The central portion of both the longitudinal vibration and the bending vibration becomes a vibration node, and the support member 3 is provided at this position. Protrusions 2a and 2b are provided at the antinodes of bending vibration. By simultaneously exciting the longitudinal vibration and the bending vibration, the protrusions 2a and 2b drive the moving body 7 by performing an elliptical motion consisting of a displacement in the longitudinal direction of the laminated vibrator 1 and a displacement in the width direction perpendicular thereto. By the way, although the example using the longitudinal primary mode and the bending secondary mode is shown here, the order of the two vibration modes is not limited, and modes of other orders may be used. Further, the positions of the protrusions 2a and 2b are not limited to the present embodiment, and may be provided on the end face in the longitudinal direction of the vibrating body. Further, the movable body 7 may be fixed and the laminated piezoelectric element 1 may be moved.
[0011]
The laminated piezoelectric elements 1, 20, 26, and 32 of the present invention will be described in detail below, but the common purpose is to efficiently excite the bending vibration, and at least the bending vibration that maximizes the distortion of the bending vibration. An electrode is provided so that the driving force works near the antinode position (position 9 in FIG. 2B) and near the end face in the width direction of the vibrator.
[0012]
(Embodiment 1)
The structure of the laminated piezoelectric element 1 will be described with reference to FIGS. As shown in FIG. 4B, the laminated piezoelectric element 1 is formed by laminating piezoelectric elements 10, 11, 12, and 13 and sintering them integrally. As shown in FIG. 3A, the upper surface of the plate-like piezoelectric element 10 is provided with four internal electrodes 14a, 14b, 14c, and 14d that are substantially divided at the center of each side. As shown in FIG. 3, an internal electrode 14 e is provided almost entirely on the upper surface of the piezoelectric element 11, and as shown in FIG. 4f, and as shown in FIG. 4A, external electrodes 15a, 15d, 15c, 15f, which are short-circuited with the internal electrodes 14a, 14b, 14c, 14d, 14e, 14f, are provided on the upper surface of the piezoelectric element 13. 15b and 15e are provided.
[0013]
In the laminated piezoelectric element 1, the electrode 14 e is GND, and the portion of the piezoelectric element sandwiched between the electrodes 14 a, 14 b, 14 c, 14 d and the electrode 14 e excites bending vibration, and the portion of the piezoelectric element sandwiched between the electrode 14 f and the electrode 14 e Excites longitudinal vibration. Accordingly, the electrodes are provided so that the driving force acts to the end surface in the width direction of the vibrating body in the range including the vicinity of the position of the antinode of bending vibration (position 9 in FIG. 2B). However, although the polarization directions of the piezoelectric elements are all in the thickness direction, the piezoelectric element in the portion sandwiched between the internal electrodes 14a and 14d and the internal electrode 14e and the piezoelectric element in the portion sandwiched between the internal electrodes 14b and 14c and the internal electrode 14e. Are polarized in the opposite direction.
[0014]
Next, a method for conducting the internal electrodes 14a, 14b, 14c, 14d, 14e, and 14f of the multilayer piezoelectric element 1 to the outside will be described. FIG. 4A is a view of the top surface and the side surface of the multilayer piezoelectric element 1. Here, the external electrodes 15 a, 15 d, 15 c, 15 f, 15 b, 15 e are short-circuited with the internal electrodes 14 a, 14 b, 14 c, 14 d, 14 e, 14 f, and supply drive signals to the laminated piezoelectric element 1. In the laminated piezoelectric element 1, the internal electrodes 14a, 14b, 14c, and 14d are provided with lead portions 14a ′, 14b ′, 14c ′, and 14d ′ in the longitudinal direction, and the internal electrode 14e is provided with a lead portion 14e ′. The internal electrode 14f is provided with a lead portion 14f ′, and each lead portion is short-circuited to the external electrodes 15a, 15d, 15c, 15f, 15b, 15e at the longitudinal end face of the multilayer piezoelectric element 1, and further, the multilayer piezoelectric element. 1 is connected to the external electrodes 15a, 15d, 15c, 15f, 15b, and 15e provided on the upper surface of the piezoelectric element 13.
[0015]
A method for driving the multilayer piezoelectric element 1 will be described. Bending vibration is generated in the laminated piezoelectric element 1 serving as a vibrating body that applies a signal having a predetermined frequency between the external electrodes 15a, 15c, 15d, and 15f and the external electrode 15b. Further, when a drive signal having a predetermined frequency is applied between the external electrode 15e and the external electrode 15b, longitudinal vibration is generated in the laminated piezoelectric element 1. Therefore, by changing the phase of the drive signal applied between the external electrodes 15a, 15c, 15d, 15f and the external electrode 15b and the drive signal applied between the external electrode 15e and the external electrode 15b, a laminated piezoelectric film that becomes a vibrating body. Since the side surface of the element 1 is elliptically moved, the moving body 7 in contact with the protrusions 2 a and 2 b provided on the laminated piezoelectric element 1 moves. By reversing the phase difference between the two signals, the direction of the elliptical motion is also reversed, so the moving direction of the moving body 7 also changes. By the way, the application method of these signals is not limited to this, and may be changed according to the polarization direction of the piezoelectric element. Conversely, the polarization direction of the piezoelectric element is also arbitrary. For example, all the polarization directions of the piezoelectric element 10 may be the same direction.
[0016]
By the way, although the example which short-circuited each internal electrode and pulled out outside was shown on the side surface of the laminated piezoelectric element 1 above, the means is not limited. Do not provide internal electrode short-circuit means or external conduction means near the position where the distortion of the desired vibration mode is maximum, that is, make sure that the force generated by the piezoelectric element is applied near the position where the distortion is maximum. It is an object of the present invention to construct internal electrodes. Therefore, in other words, the internal electrodes may be short-circuited and connected to the outside in the vicinity of the position where the distortion is minimized. For example, a minute hole (through hole) may be provided in the thickness direction of the piezoelectric element, a conductive material may be embedded in the hole, and the internal electrode may be short-circuited or electrically connected to the outside. In that case, it is preferable to provide the hole at the central portion in the width direction which is the neutral surface of the displacement of bending vibration, avoiding the vicinity of the end surface in the width direction of the multilayer piezoelectric element 1, or at the end surface in the longitudinal direction. Longitudinal end surfaces do not generate longitudinal vibration distortion, so that large vibrations can be excited in both bending vibration and longitudinal vibration without affecting longitudinal vibration excitation. In this case, the internal electrode can be provided up to the end in the width direction of the laminated piezoelectric element.
[0017]
5 and 6 show another example of the laminated piezoelectric element according to the embodiment of the present invention. As shown in FIG. 6B, the laminated piezoelectric element 20 is formed by laminating piezoelectric elements 16, 17, 18, and 19 and sintering them integrally. As shown in FIG. 5A, on the upper surface of the plate-like piezoelectric element 16, four internal electrodes 21a, 21b, 21c, and 21d divided substantially at the center of each side are provided. As shown in FIG. 5, an internal electrode 21e is provided almost entirely on the upper surface of the piezoelectric element 17, and as shown in FIG. As shown in FIG. 6 (a), the upper surface of the piezoelectric element 19 is provided with external electrodes 22b, 22c, 22e, 22f, and 22a that are short-circuited with the internal electrodes 21a, 21b, 21c, 21d, 21e, and 21f. , 22d are provided.
[0018]
In the laminated piezoelectric element 20, the electrode 21e is GND, and the piezoelectric element in the portion sandwiched between the electrodes 21a, 21b, 21c, 21d and the electrode 21e excites bending vibration, and the piezoelectric element in the portion sandwiched between the electrode 21f and the electrode 21e. Excites longitudinal vibration. Accordingly, the electrodes are provided so that the driving force acts to the end surface in the width direction of the vibrating body in the range including the vicinity of the position of the antinode of bending vibration (position 9 in FIG. 2B). For example, in the electrodes 21e and 21f, no electrode is provided in the vicinity of the end face in the width direction of the central portion. This will be described later when the electrodes 21a, 21b, 21c and 21d are short-circuited with the external electrodes. This is a margin for avoiding a short circuit with the electrodes 21e and 21f, and this portion does not generate a driving force, but a portion having a small distortion of bending vibration and an influence on the driving force is extremely small. However, although the polarization directions of the piezoelectric elements are all in the thickness direction, the piezoelectric element in the portion sandwiched between the internal electrodes 21a, 21d and the internal electrode 21e and the piezoelectric portion in the portion sandwiched between the internal electrodes 21b, 21c and the internal electrode 21e. The element is polarized in the opposite direction.
[0019]
Next, a method of conducting the internal electrodes 21a, 21b, 21c, 21d, 21e, and 21f of the multilayer piezoelectric element 20 to the outside will be described. FIG. 6A is a view of the top surface and the side surface of the laminated piezoelectric element 20. Here, the external electrodes 22b, 22c, 22e, 22f, 22a, and 22d are short-circuited with the internal electrodes 21a, 21b, 21c, 21d, 21e, and 21f, and supply drive signals to the laminated piezoelectric element 20. In the laminated piezoelectric element 20, the internal electrodes 21a, 21b, 21c, and 21d are nodes of bending vibration, and the external electrodes 22b, 22b, 22c, 22e, and 22f are short-circuited, and the internal electrodes 21e and 21f are short-circuited to the external electrodes 22a and 22d, respectively, at one end in the longitudinal direction. Further, external electrodes provided on the upper surface of the laminated piezoelectric element 20, that is, the upper surface of the piezoelectric element 19 The electrodes 22b, 22c, 22e, 22f, 22a and 22d are electrically connected.
[0020]
A method for driving the laminated piezoelectric element 20 will be described. Bending vibration is generated in the laminated piezoelectric element 20 serving as a vibrating body that applies a signal having a predetermined frequency between the external electrodes 22b, 22c, 22e, and 22f and the external electrode 22a. Further, when a drive signal having a predetermined frequency is applied between the external electrode 22d and the external electrode 22a, longitudinal vibration is generated in the laminated piezoelectric element 20. Therefore, by changing the phase of the drive signal applied between the external electrodes 22b, 22c, 22e, and 22f and the external electrode 22a and the phase of the drive signal applied between the external electrode 22d and the external electrode 22a, a laminated piezoelectric film that becomes a vibrating body. Since the side surface of the element 20 is elliptically moved, the moving body 7 in contact with the protrusions 2a and 2b provided on the laminated piezoelectric element 20 moves. By reversing the phase difference between the two signals, the direction of the elliptical motion is also reversed, so the moving direction of the moving body 7 also changes.
[0021]
(Embodiment 2)
7 and 8 show a second example of the laminated piezoelectric element of the ultrasonic motor of the present invention. As shown in FIG. 8B, the laminated piezoelectric element 26 is formed by laminating piezoelectric elements 23, 24, and 25 and sintering them integrally. As shown in FIG. 7A, on the upper surface of the plate-like piezoelectric element 23, internal electrodes 27c are provided in the longitudinal direction at the central portion in the width direction, and at the central portions in the longitudinal direction on both sides in the width direction. Divided four internal electrodes 27a, 27b, 27d, and 27e are provided. As shown in FIG. 7B, the entire upper surface of the piezoelectric element 24 is provided with an internal electrode 27f. As shown in FIG. 5A, external electrodes 28a, 28d, 28c, 28f, 28b, and 28e that are short-circuited with the internal electrodes 27a, 27b, 27d, 27e, 27c, and 27f are provided on the upper surface of the piezoelectric element 25. .
[0022]
In the laminated piezoelectric element 26, the internal electrode 27f is GND and the portion of the piezoelectric element sandwiched between the electrodes 27a, 27b, 27d, and 27e excites bending vibration, and the portion of the piezoelectric element sandwiched between the internal electrode 27f and the electrode 27c. The element excites longitudinal vibration. Accordingly, the electrodes are provided so that the driving force acts to the end surface in the width direction of the vibrating body in the range including the vicinity of the position of the antinode of bending vibration (position 9 in FIG. 2B). Therefore, the piezoelectric element does not generate a driving force in the vicinity of the end portion in the longitudinal direction, but this portion has a very small effect not only for bending vibration but also for excitation of longitudinal vibration. Incidentally, as will be described later, this is a margin for avoiding short-circuiting of internal electrodes other than the intended purpose when short-circuiting the internal electrode 27 and the external electrode 28. However, although the polarization directions of the piezoelectric elements are all in the thickness direction, the piezoelectric element in the portion sandwiched between the internal electrodes 27a and 27e and the internal electrode 27f and the piezoelectric element in the portion sandwiched between the internal electrodes 27d and 27b and the internal electrode 27f. Are polarized in the opposite direction.
[0023]
Next, a conduction method to the outside of the internal electrode 27 of the laminated piezoelectric element 26 will be described. FIG. 8A is a view of the top surface and the side surface of the laminated piezoelectric element 26. Here, the external electrodes 28a, 28d, 28c, 28f, 28b, and 28e are short-circuited with the internal electrodes 27a, 27b, 27d, 27e, 27c, and 27f, and supply drive signals to the laminated piezoelectric element 26. In the laminated piezoelectric element 26, the internal electrodes 27a, 27c, 27d, 27b, 27f, and 27e are short-circuited with the external electrodes 28a, 28b, 28c, 28d, 28e, and 28f in the vicinity of the end faces in the longitudinal direction, respectively. Electrical conduction is provided to the upper surface, that is, the external electrodes 28a, 28b, 28c, 28d, 28e, and 28f provided on the upper surface of the piezoelectric element 25.
[0024]
A method for driving the multilayer piezoelectric element 26 will be described. Bending vibration is generated in the laminated piezoelectric element 26 serving as a vibrating body that applies a signal of a predetermined frequency between the external electrodes 28a, 28c, 28d, 28f and the external electrode 28e. When a drive signal having a predetermined frequency is applied between the external electrode 28b and the external electrode 28e, longitudinal vibration is generated in the laminated piezoelectric element 26. Here, by changing the phases of the drive signal applied between the external electrodes 28a, 28c, 28d, and 28f and the external electrode 28e and the drive signal applied between the external electrode 28b and the external electrode 28e, a laminated piezoelectric film that becomes a vibrating body. Since the side surface of the element 26 is elliptically moved, the moving body 7 in contact with the protrusions 2 a and 2 b provided on the laminated piezoelectric element 26 moves. By reversing the phase difference between the two signals, the direction of the elliptical motion is also reversed, so the moving direction of the moving body 7 also changes.
[0025]
(Embodiment 3)
The configuration of the laminated piezoelectric element 32 according to the third embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 10B, the laminated piezoelectric element 32 is formed by laminating piezoelectric elements 29, 30, and 31 and sintering them integrally. As shown in FIG. 9A, the upper surface of the plate-like piezoelectric element 29 is provided with four internal electrodes 33a, 33b, 33c, and 33d that are substantially divided at the center of each side. As shown in FIG. 10, an inner electrode 33e is provided almost entirely on the upper surface of the piezoelectric element 30, and as shown in FIG. 10A, the inner electrodes 33a, 33b, 33c, External electrodes 34a, 34d, 34c, 34f, and 34b that are short-circuited with 33d and 33e are provided.
[0026]
In the laminated piezoelectric element 32, the electrode 33e becomes GND, and the piezoelectric element in the portion sandwiched between the electrodes 33a, 33b, 33c, 33d and the electrode 33e excites longitudinal vibration and bending vibration. Accordingly, the electrodes are provided so that the driving force works to the end surface in the width direction of the vibrating body in the range including the vicinity of the position of the antinode of bending vibration (position 9 in FIG. 2B). However, the polarization directions of the piezoelectric elements are all polarized in the same direction in the thickness direction.
[0027]
Next, a method for conducting the internal electrodes 33a, 33b, 33c, 33d, and 33e of the laminated piezoelectric element 32 to the outside will be described. FIG. 10A is a view of the top surface and the side surface of the laminated piezoelectric element 32. Here, the external electrodes 34a, 34d, 34c, 34f, and 34b are short-circuited with the internal electrodes 33a, 33b, 33c, 33d, and 33e, and supply drive signals to the laminated piezoelectric element 32. In the laminated piezoelectric element 32, the internal electrodes 33a, 33b, 33c, and 33d are provided with lead portions 33a ′, 33b ′, 33c ′, and 33d ′ in the longitudinal direction and end portions in the width direction, and the internal electrodes 33e are provided with longitudinal end surfaces. A lead portion 33 e ′ is provided at the center, and each lead portion is short-circuited with the external electrodes 34 a, 34 d, 34 c, 34 f, 34 b at the longitudinal end face of the multilayer piezoelectric element 32, and further, the top surface of the multilayer piezoelectric element 32. That is, conduction is made to the external electrodes 34a, 34d, 34c, 34f, 34b provided on the upper surface of the piezoelectric element 31.
[0028]
There are two methods for driving the laminated piezoelectric element 32, for example, as follows. By applying a drive signal between the external electrodes 34 a and 34 f and the external electrode 34 b or between the external electrodes 34 c and 34 d and the external electrode 34 b, longitudinal vibration and bending vibration are excited in the laminated piezoelectric element 32. By switching the electrode to which the drive signal is applied, the phases of the longitudinal vibration and the bending signal are reversed, and the moving direction of the moving body 7 is also changed. As another method, the external electrode 34b is set to GND, and drive signals having different phases, for example, signals different from each other by 90 degrees or −90 degrees, are applied between the external electrodes 34a and 34f and the external electrodes 34c and 34d. A longitudinal vibration and a bending vibration are excited at 32. By reversing the phase, the phases of the longitudinal vibration and the bending signal are reversed, and the moving direction of the moving body 7 also changes.
[0029]
(Embodiment 4)
An example in which an electronic apparatus is configured using the piezoelectric actuator of the present invention will be described with reference to FIG.
[0030]
FIG. 11 is a block diagram in which an ultrasonic motor 100 driven by a drive circuit of the present invention is applied to a drive source of an electronic device. The multilayer piezoelectric elements 1, 20, 26, and 32 and the multilayer piezoelectric element 1 are shown in FIG. , 20, 26, 32, the friction member 2 contacting the moving body 7 by the pressurizing means 6, the moving body 7 frictionally driven by them, the transmission mechanism 35 operating integrally with the moving body 7, and the transmission mechanism The output mechanism 36 operates based on the operation 35. Here, an example in which the moving body is a rotating body and the moving body is rotated will be described.
[0031]
Here, the transmission mechanism 35 uses, for example, a transmission wheel such as a gear train or a friction wheel. The output mechanism 36 includes a paper feed mechanism in a printer, a shutter drive mechanism, a lens drive mechanism, a film winding mechanism in a camera, a pointer in an electronic device and a measuring instrument, an arm mechanism in a robot, and a machine tool. In this case, a tooth tool feeding mechanism, a processing member feeding mechanism, or the like is used.
[0032]
Note that an electronic timepiece, a measuring instrument, a camera, a printer, a printing machine, a robot, a machine tool, a game machine, an optical information device, a medical device, a moving device, and the like can be realized as the electronic device in this embodiment.
[0033]
Furthermore, if the moving body 7 is provided with an output shaft and has a power transmission mechanism for transmitting torque from the output shaft, an ultrasonic motor driving device can be realized. If the stage is configured as an ultrasonic motor driving device, the mechanism is simpler and smaller than a stage using an ordinary electromagnetic motor, and the stage uses an ultrasonic motor that can be used even in an environment avoiding magnetization. Can be provided.
[0034]
【The invention's effect】
According to the present invention, the elliptical of a vibrating body that generates low-voltage drive characteristics by using a multilayer piezoelectric element, in particular, can efficiently excite bending vibration, and is generated by the combination of longitudinal vibration and displacement of bending vibration, and produces output. The shape of the motion ellipse is close to a perfect circle, and a large thrust can be obtained and a highly efficient ultrasonic motor can be realized. Since this effect becomes remarkable when the vibrating body is downsized, a small and high output ultrasonic motor can be realized. In addition, by using an ultrasonic motor provided with these vibrators as a drive source of an electronic device, the electronic device can be reduced in size, thickness, and power consumption.
[0035]
Further, if the moving body of the ultrasonic motor of the present invention is directly provided with an output member such as a lens or a pointer, or if the output member is moved through the transmission mechanism, the zoom mechanism, autofocus mechanism or watch of the camera is moved. It can be applied to electronic devices such as
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration relating to an ultrasonic motor of the present invention.
FIG. 2 is a diagram showing a vibration mode of a vibrating body related to the ultrasonic motor of the present invention.
FIG. 3 is a diagram showing a configuration of a vibrating body of the ultrasonic motor according to the first embodiment of the present invention.
FIG. 4 is a diagram showing a configuration of a vibrating body of the ultrasonic motor according to the first embodiment of the present invention.
FIG. 5 is a diagram showing another configuration of the vibrating body of the ultrasonic motor according to the first embodiment of the present invention.
FIG. 6 is a diagram showing another configuration of the vibrator of the ultrasonic motor according to the first embodiment of the present invention.
7 is a diagram showing a configuration of a vibrating body of an ultrasonic motor according to a second embodiment of the present invention. FIG.
FIG. 8 is a diagram illustrating a configuration of a vibrating body of an ultrasonic motor according to a second embodiment of the present invention.
FIG. 9 is a diagram showing a configuration of a vibrating body of an ultrasonic motor according to a third embodiment of the present invention.
FIG. 10 is a diagram showing a configuration of a vibrating body of an ultrasonic motor according to a third embodiment of the present invention.
FIG. 11 is a diagram showing an electronic apparatus using the ultrasonic motor of the present invention.
[Explanation of symbols]
1, 20, 26, 32 Multilayer Piezoelectric Element 2 Protrusion 3 Support Member 6 Pressure Spring 7 Moving Body

Claims

面内方向に屈曲振動を励振する複数の圧電素子を前記面内方向と直交する方向に積層して矩形形状の振動体を構成し、前記振動体と接する移動体を駆動する超音波モータにおいて、
屈曲振動を励振する前記圧電素子の内部電極は、前記面内方向と直交する方向の二つの面に設けられ、この二つの面に設けられた内部電極は前記屈曲振動の腹に位置する部分においては前記振動体の幅方向端部において前記積層の方向に重なるように設けられ、
前記複数の圧電素子間の界面に設けられた前記屈曲振動を励振する内部電極を短絡する外部電極は前記振動体の幅方向端面の前記二つの面に設けられた内部電極同士が重ならない位置であって前記振動体に発生する屈曲振動の腹となる位置近傍を避ける位置に設けられていることを特徴とする超音波モータ。 In an ultrasonic motor that drives a moving body in contact with the vibrating body by forming a rectangular vibrating body by laminating a plurality of piezoelectric elements that excite bending vibration in an in- plane direction in a direction orthogonal to the in-plane direction .
Internal electrodes of the piezoelectric element for exciting the flexural vibration is provided on two surfaces in the direction perpendicular to the plane direction, the internal electrodes provided on the two faces in the portion located on the ventral of the bending vibration Is provided so as to overlap the direction of the stacking at the end in the width direction of the vibrator,
The external electrode for short-circuiting the internal electrode for exciting the bending vibration provided at the interface between the plurality of piezoelectric elements is located at a position where the internal electrodes provided on the two surfaces of the width direction end surface of the vibrating body do not overlap each other. An ultrasonic motor, wherein the ultrasonic motor is provided at a position that avoids the vicinity of a position that becomes an antinode of bending vibration generated in the vibrating body.

前記屈曲振動の腹は前記振動体の長手方向の端部以外の腹であることを特徴とする請求項１記載の超音波モータ。 The ultrasonic motor according to claim 1, wherein the antinode of the bending vibration is an antinode other than an end portion in a longitudinal direction of the vibrating body.

前記内部電極は前記振動体の幅方向端面であって長手方向の中央部で前記外部電極と短絡されていることを特徴とする請求項１記載の超音波モータ。 2. The ultrasonic motor according to claim 1, wherein the internal electrode is short-circuited to the external electrode at a central portion in a longitudinal direction, which is an end face in the width direction of the vibrating body.

前記内部電極は前記振動体の長手方向端部近傍で短絡されていることを特徴とする請求項１記載の超音波モータ。 The ultrasonic motor according to claim 1, wherein the internal electrode is short-circuited in the vicinity of a longitudinal end portion of the vibrating body.

請求項１から４のいずれかに記載の超音波モータを備えた電子機器。 The electronic device provided with the ultrasonic motor in any one of Claim 1 to 4.

請求項１から４のいずれかに記載の超音波モータを備えたステージ。 A stage comprising the ultrasonic motor according to claim 1.